English

• The rapid development of wearable and portable electronic products has brought new challenges to the design of flexible energy storage devices (FESDs) that are low-cost, high-security, great electrochemical performance, and strong mechanical flexibility [1–3]. Among various options, aqueous Zn-ion batteries (AZIBs) are recognized as promising candidates for FESDs due to the advantages of Zn anodes, including high theoretical capacity (820 mAh/g and 5855 mAh/cm³), low redox potential (−0.762 V vs. SHE), abundant resources, and environmental compatibility [4–7]. However, the development and application of AZIBs in FESDs are hindered by two issues related to the metallic Zn anode: (1) Uncontrolled growth of Zn dendrites due to uneven nucleation and poor reversibility of Zn plating/stripping, which can lead to internal short circuits [8–10] (2) Dense Zn foils with low specific surface area and unsatisfactory reaction sites impede the redox kinetics of Zn↔Zn²⁺, and their inherent rigidity limits flexibility, making them unsuitable for the unique application scenarios of FESDs [11,12].

  Recently, it has been considered an ideal strategy to integrate carbon-based conductive frameworks with Zn-based nanostructured materials to design high-performance Zn anodes [13]. However, issues, such as the inevitable lattice mismatch between carbon and Zn atoms and inappropriate regulation of zincophilic sites, may create high energy barriers for Zn nucleation, leading to irreversible Zn plating/stripping on the substrate. According to the previous studies, graphene can form a low lattice mismatch interface with the Zn(002) plane [14], and the heteroatom doping can modulate zincophilic sites [15,16], inducing more uniform Zn deposition. However, the relationship between Zn deposition and interfacial properties remains unclear, which significantly impacts the reversibility of Zn plating/stripping. Here, we develop a heteroatom doping strategy integrating graphene-like interfacial construction (Scheme S1 in Supporting information) to systematically investigate the influence of zincophilic sites and surface electric fields on Zn deposition. Density functional theory (DFT) calculations and finite element simulations reveal that sulfur-doped graphene-like network (S-GP) shows moderate zincophilicity and even electric field distribution, which can enhance the reversibility of Zn plating/stripping and thus improve long-term cycling stability. Importantly, the flexible ZIBs based on S-GP substrate demonstrate great electrochemical and mechanical performance, indicating its potential applications in portable/wearable electronic devices.

  The macroscopical states of produced samples are displayed by digital photo in Fig. S1 (Supporting information), and the flexibility of S-GP is verified in Fig. S2 (Supporting information). The morphology of the prepared samples is initially characterized by SEM. After doping, aggregated nanosheets transform into loose ones (Fig. 1a and Fig. S3 in Supporting information), providing more active sites for Zn nucleation and a soft substrate for Zn deposition (as proved by electroactive surface areas in Fig. S4 in Supporting information), thereby enhancing the cycling stability of the Zn anode. As expected, the doped GP surface is covered with a uniform Zn layer without apparent agglomerated particles (Fig. 1b, Figs. S3d, f and h in Supporting information), whereas O-GP@Zn exhibits an accumulative morphology with Zn-based nanosheets growing large and upright (Fig. S3b in Supporting information). Further investigation of its morphology and phase information was carried out through TEM testing in Fig. 1c, a mixed structure consisting of large and small nanosheets is observed, with the small nanosheets evenly dispersed on the large nanosheets. HRTEM (inset image of Fig. 1d) confirms that the large nanosheets exhibit the interplanar distance of 0.34 nm for the graphene-like carbon, while the small nanosheets reveal a layer spacing of 0.25 nm corresponding to the (002) plane of Zn [17]. X-ray diffraction (XRD) patterns in Fig. S5 (Supporting information) also support this mixed phase and composition. In Fig. 1e, a homogeneous distribution of C, O, S, and Zn elements is detected, indicating uniform S doping and Zn deposition.

  Figure 1

  

  Figure 1.  Scanning electron microscopy (SEM) images of (a) S-GP and (b) S-GP@Zn. (c) Transmission electron microscopy (TEM), inset image is high-resolution transmission electron microscopy (HRTEM), and (d) EDS mapping of S-GP@Zn. (e) Fourier transform infrared (FT-IR) and (f) Raman spectra of O-GP, N-GP, S-GP, and P-GP. (g) S 2p spectrum of S-GP.

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  The surface chemical properties were analyzed through spectroscopy, in FTIR (Fig. 1e), a broad peak around 3324 cm⁻¹ for O-GP is attributed to the stretching vibration of -OH. Some functional groups appearing between 790 cm⁻¹ and 1760 cm⁻¹ are related to the C-O and C=O stretching vibrations of graphene oxide [18]. After N/P/S doping, the intensity of these oxygen functional groups is reduced, potentially enhancing the material’s conductivity. The structural characterization was further elucidated through Raman spectroscopy in Fig. 1f. The peaks at 1352 cm⁻¹ and 1601 cm⁻¹ correspond to the D band and G band, respectively, reflecting carbon disorder and graphitization degree. The intensity ratio (I_D/I_G) in N/S/P-GP (0.98) is higher than in O-GP (0.88), indicating the formation of a significant amount of defects or vacancies after doping [19]. Furthermore, the X-ray photoelectron spectroscopy (XPS) in Figs. S6 and S7 (Supporting information) confirms the presence of heteroatoms in different samples. Moreover, the C 1s spectra in Fig. S8 (Supporting information) and the heteroatom spectra in Fig. 1g, Figs. S9 and S10 (Supporting information) demonstrate the connectivity between C and heteroatoms, for example, the S 2p spectrum (Fig. 1g) can be decomposed into three peaks corresponding to S-C/S=O, S 2p_3/2, and S 2p_1/2, with binding energies of 167.7, 165.5, and 163.7 eV, respectively [20]. The S 2p_1/2 and S 2p_3/2 arise from the C-S bond. These functional groups can enhance the wettability of the samples, as evidenced by the contact angle of electrolyte droplets on different substrates in Fig. S11 (Supporting information), facilitating uniform Zn nucleation and rapid ion/electron transfer.

  To investigate the impact of doped atoms on the Zn plating process, DFT calculations were applied [21]. The optimized models and results in Fig. 2a and Figs. S12-S17 (Supporting information) show a binding energy of −0.292 eV between Zn²⁺ and Spd, which is higher than carbon and other functional groups but lower than pyrrolic N (Npr, −0.488 eV) and quaternary N (Nq, −0.294 eV). Due to the suitable binding energy of Spd, S-GP samples can facilitate the rapid nucleation and growth of Zn²⁺ during the plating process and achieve reversible Zn stripping, demonstrating potential advantages in enhancing cyclic stability. Additionally, the local charge density between Zn and heteroatom-functionalized samples also reveals that Spd can retain intermediate electrons, as shown in Fig. 2b and Figs. S12-S17, further proving the richness and proper activity of samples doped with Spd for preferential deposition of Zn metal and highly reversible Zn plating/stripping processes.

  Figure 2

  

  Figure 2.  (a) The binding energy of Zn atom with graphene (G) and different functional groups. (b) The charge density differences for Zn²⁺ adsorbed on pyridinic S (Spd) group, the yellow and light royal blue areas present the negative and positive charge differences. Models of the electric field distributions for (c) Zn foil and (d) S-GP@Zn. SEM images of S-GP anode during the Zn plating process at 5 mA/cm² with (e) 5 mAh/cm², (f) 10 mAh/cm², and (g) 20 mAh/cm², and (h) the corresponding schematic diagram of morphology evolution.

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  Additionally, finite element simulation was used to explore the advantage of S-functional groups in controlling the interfacial electric field distribution [21,22]. During the electrodeposition process on Zn foil, an electric field distribution with a noticeable gradient of charge accumulation is formed. The non-uniform electric field distribution leads to preferential nucleation and growth of Zn atoms in high charge regions, resulting in the “tip effect” (Fig. 2c). Due to this detrimental effect, small protrusions gradually develop into large dendritic flakes, ultimately leading to a short circuit in the battery. In contrast, the electronic conductivity and charge redistribution effects of S-functional groups result in a more uniform interface electric field (Fig. 2d). The even electric field distribution of S-GP ensures the homogeneous nucleation and diffusion of Zn atoms, leading to a flat deposition surface. Therefore, introducing S-functional groups into the S-GP matrix is a good strategy to achieve uniform Zn nucleation, guide the growth of Zn atoms, and thus realize the manufacture of dendrite-free anodes.

  The morphological evolution during Zn plating is illustrated to demonstrate the superiority of S-doping in the Zn deposition in Figs. 2e-g and Fig. S18 (Supporting information). Through S doping, S-GP substrates with more effective zincophilic S functional groups and loose surfaces, were prepared, inducing selective Zn nucleation. Zn nanosheets cover S-GP substrates uniformly with smaller dimensions, without aggregation of Zn dendrites at a deposition capacity of 5 mAh/cm² (Fig. 2e). After reaching 10 mAh/cm², dense Zn nanosheets completely cover the surface of S-GP (Fig. 2f). As the capacity increases to 20 mAh/cm² (Fig. 2g), some Zn nanosheets cover the S-GP surface with clear underlying framework, indicating the superiority of S-GP in withstanding high-capacity Zn deposition, which is further validated at 1 mA/cm² with 10 mAh/cm² in Fig. S19 (Supporting information). Benefiting from the appropriate binding energy and uniform electric field distribution, the surface of S-GP possesses even Zn²⁺ flux, inducing more uniform Zn depostion (Fig. 2h).

  The comparison of the Zn-plated morphology reveals that the S-GP can reduce the nucleation resistance of Zn and inhibit side reactions, as proved by the lower nucleation overpotential (Fig. S20 in Supporting information), improved reaction kinetics (Fig. S21 in Supporting information), and lower voltage of HER and Zn deposition (Fig. S22 in Supporting information). Also, the S-GP electrode demonstrates a higher initial coulombic efficiency (CE) and a more stable state in subsequent cycles in Figs. S23 and S24 (Supporting information). Further XRD analyses suggest the preferential Zn(002) lattice plane deposition (Table S1 in Supporting information) and the less produced Zn₄SO₄(OH)₆·xH₂O byproducts (Fig. S25 in Supporting information) on the S-GP surface. All of the results imply that S-doping can induce appropriate zincophilicity, even electric field distribution, and thus regulate the Zn²⁺ flux, thereby achieving uniform and compact Zn deposition.

  Electrochemical impedance spectroscopy (EIS) measurements were conducted to quantitatively estimate the deposition kinetics of Zn²⁺ ions based on the desolvation activation energy (E_a), calculated from the values of Nyquist plots (Figs. S26 and S27, Table S2 in Supporting information). As shown in Fig. 3a, N/P/S doped electrodes exhibit similar E_a values, significantly lower than those of Zn (32.18 kJ/mol) and O-GP@Zn (28.95 kJ/mol) anodes. This indicates that the N/P/S elements greatly enhance the deposition kinetics of Zn and facilitate the transfer of Zn²⁺ ions. Furthermore, the Zn plating/stripping performance was studied in Fig. 3b, demonstrating the cells with the S-GP@Zn electrode exhibit longer cycling stability, with the voltage profile remaining stable over 500 h. Other electrodes show inferior stability, and more pronounced comparisons are also observed at different current densities of 1 mA/cm² and 2 mA/cm² (Fig. S28 in Supporting information), where the significant voltage fluctuations as well as cells’ failure after a short cycling time can be observed for Zn foil and O/N/P-GP@Zn electrodes. Fig. 3c presents the rate performance of cells, further illustrating the stable voltage profile of the S-GP@Zn battery. After adjusting the current density to a lower value, the voltage hysteresis can recover well, indicating high reversibility and stability of the S-GP@Zn anode. The superior reversibility of the S-GP@Zn anode indicates the favorable Zn²⁺ transfer kinetics, which is proved by the highest i₀ value (7.85 mA/cm²) in Fig. 3d and Fig. S29 (Supporting information) [23]. Furthermore, the low semicircle at high frequency before and after cycling further verifies the great cycling stability of the prepared S-GP electrode (Fig. S30 in Supporting information). The cycling stability and voltage hysteresis of the prepared S-GP demonstrate superiority over various reported Zn-based hosts, as shown in Fig. 3e [16,24–29].

  Figure 3

  

  Figure 3.  Reversible Zn plating/stripping performance with Zn, O-GP@Zn, N-GP@Zn, P-GP@Zn, and S-GP@Zn anodes. (a) E_a values of different cells. (b) Comparison of voltage profiles at 0.5 mA/cm² with 0.25 mAh/cm². (c) Rate performance. (d) The corresponding exchange current densities (i₀). (e) Performance comparison chart with other works. (f) CE of Zn//Cu cells. (g) The corresponding voltage profiles at different cycles.

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  In Fig. 3f, the reversibility of different prepared anodes was studied through CE. Due to the impact of binding energy, S-GP@Zn exhibits moderate initial CE, lower than N-GP@Zn but higher than other anodes, and shows a stable Zn plating/stripping process in subsequent cycles, revealing its superior intrinsic reversibility and Zn²⁺ deposition/dissolution kinetics [30]. After 20 cycles, the CE of S-GP@Zn reaches 90.9% at 1 mA/cm², higher than O-GP@Zn and N-GP@Zn, and more stable than P-GP@Zn, further illustrating the effective promotion of S-functional groups on the Zn plating/stripping process. Additionally, as shown in Fig. 3g and Fig. S31 (Supporting information), S-GP@Zn demonstrates the stable voltage separation based on the plateau overpotential at 1 mA/cm², around 56.1 mV. The presented results confirm that S-functional groups on S-GP can provide abundant Zn²⁺ nucleation sites, improve Zn²⁺ transport kinetics, and mitigate side reactions, thereby stabilizing the Zn plating/stripping process.

  The flexible cells were assembled to explore the practical application of anodes by coupling with MnO_x cathodes. XRD patterns prove the successful deposition of MnO_x on different substrates in Fig. S32 (Supporting information). SEM images in Fig. S33 (Supporting information) reveal the interconnected, loosely packed, and vertically aligned nanofibers are produced on the S-GP surface, facilitating electron/ion transfer and enhancing the energy storage performance of the MnO_x material. To highlight the superiority of S doping, the CV curves of Zn-Mn batteries based on different substrates are compared in Fig. 4a, showing distinct redox peaks corresponding to the Mn²⁺/MnO_x deposition/dissolution as well as the H⁺ insertion/extraction mechanisms in MnO_x [31,32]. The S-GP@MnO_x cathode exhibits the highest capacity and the lowest peak gap of 0.33 V, indicating its better reversibility. Compared to Zn-Mn batteries based on O-GP, those based on S-GP show higher capacities at all measured current densities (Fig. 4b and Fig. S34 in Supporting information), demonstrating satisfactory rate performance. Furthermore, the capacity can return to its initial value when the current density is recovered to 0.3 A/g, revealing outstanding stability of the Zn-Mn battery based on S-GP. Furthermore, based on the loading mass of MnO_x, the assembled N-GP-based Zn-Mn cells deliver a maximum energy density of 156.3 Wh/kg and a maximum power density of 3560.8 W/kg, showing great comparability with other previous studies (Fig. 4c) [33–40].

  Figure 4

  

  Figure 4.  Electrochemical performance of flexible Zn-Mn battery. (a) CV curves. (b) Capacities at different current densities. (c) Ragone plots [33–40]. (d) Long-term cyclic stability. (e) Capacity retention of the Zn-Mn battery under different bending angles at 1.0 A/g.

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  In Fig. 4d, the long-term cycling stability of the full cell based on S-GP at 2 A/g was tested. After over 1500 cycles, it maintains good capacity retention of 96.1%. Additionally, after cycling over 300 cycles at 0.3 A/g, the capacity can retain 77.7% of its initial value (Fig. S35 in Supporting information). SEM images in Fig. S36 (Supporting information) indicate that the surface of the S-GP@Zn anode is still covered with graphene-like nanosheets, and the initial dense surface is observed on the S-GP@MnOx cathode after cycling, further revealing the high cycling stability. Furthermore, flexibility tests are conducted on the Zn-Mn battery based on S-GP to demonstrate its potential practical applications in FESDs. In Fig. 4e, the capacity at different bending angles can be well maintained at 1.0 A/g. More importantly, three batteries connected in series can successfully power red light-emitting diodes in both normal and bent states (Fig. S37 in Supporting information), further proving their significant application potential.

  In summary, we studied the influence of different heteroatom-doped substrates on the stability of Zn anodes, revealing the superiority of S-GP. Through DFT calculations and finite element simulations, we investigated the zincophilicity of functional groups and the electric field distribution, finding that S-GP with moderate zincophilicity, graphene-like structure, and enhanced conductivity, can facilitate uniform Zn nucleation and reversibility of Zn plating/stripping. Consequently, S-GP hosts demonstrate impressive long-term cycling stability (over 500 h), great rate performance, and stable CE. Additionally, when combined with MnO_x flexible cathodes, the prepared flexible AZIBs deliver a high capacity of up to 134.8 mAh/g, good long-term cycling stability of 96.1% after 1500 cycles, and satisfactory flexibility, suggesting promising application prospects in portable and wearable electronic devices.

  Declaration of competing interest

  The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

  CRediT authorship contribution statement

  Xiaoqin Li: Writing – original draft, Validation, Methodology, Formal analysis. Xiaohan Chen: Validation, Methodology. Yongqiang Guo: Formal analysis. Jian Xiang: Methodology. Yinkun Zhao: Data curation. Taotao Gao: Investigation. Qu Yue: Resources. Wenlong Liu: Visualization. Lu Qiu: Resources. Dan Xiao: Supervision, Funding acquisition, Conceptualization. Panpan Li: Writing – review & editing, Supervision, Funding acquisition.

  Acknowledgment

  The authors would like to thank Qin Liang from Shiyanjia Lab (www.shiyanjia.com) for the Raman and XPS analyses.

  Supplementary materials

  Supplementary material associated with this article can be found, in the online version, at doi:10.1016/j.cclet.2024.110327.

  
  
• 1. [1]

     X. Li, X. Chen, Z. Jin, et al., Mater. Chem. Front. 5 (2021) 1140–1163. doi: 10.1039/d0qm00745e

  2. [2]

     J. Zhang, C. Lin, L. Zeng, et al., Small 20 (2024) 2312116. doi: 10.1002/smll.202312116

  3. [3]

     Z. Zhu, T. Jiang, M. Ali, et al., Chem. Rev. 122 (2022) 16610–16751. doi: 10.1021/acs.chemrev.2c00289

  4. [4]

     X. Li, J. Xiang, H. Liu, et al., J. Colloid Interface Sci. 654 (2024) 476–485. doi: 10.1016/j.jcis.2023.10.057

  5. [5]

     W. Wu, Y. Deng, G. Chen, Chin. Chem. Lett. 34 (2023) 108424. doi: 10.1016/j.cclet.2023.108424

  6. [6]

     X. Zheng, Z. Liu, J. Sun, et al., Nat. Commun. 14 (2023) 76. doi: 10.1038/s41467-022-35630-6

  7. [7]

     M. Wang, Y. Meng, M. Sajid, et al., Angew. Chem. Inter. Ed. 63 (2024) e202404784. doi: 10.1002/anie.202404784

  8. [8]

     Q. Yang, Q. Li, Z. Liu, et al., Adv. Mater. 32 (2020) e2001854. doi: 10.1002/adma.202001854

  9. [9]

     M. Yang, H. Huang, S. Shen, et al., Chin. Chem. Lett. 36 (2025) 109988. doi: 10.1016/j.cclet.2024.109988

  10. [10]

      H. Lin, C. Lin, F. Xiao, et al., Adv. Funct. Mater. 34 (2024) 2310486. doi: 10.1002/adfm.202310486

  11. [11]

      Q. Li, D. Wang, B. Yan, et al., Angew. Chem. Inter. Ed. 61 (2022) e202202780. doi: 10.1002/anie.202202780

  12. [12]

      C. Wang, T. He, J. Cheng, et al., Adv. Funct. Mater. 30 (2020) 2004430. doi: 10.1002/adfm.202004430

  13. [13]

      J.L. Yang, P. Yang, W. Yan, et al., Energy Storage Mater. 51 (2022) 259–265. doi: 10.1016/j.ensm.2022.06.050

  14. [14]

      J. Zheng, Q. Zhao, T. Tang, et al., Science 366 (2019) 645–648. doi: 10.1126/science.aax6873

  15. [15]

      K. Liu, H. Li, M. Xie, et al., J. Am. Chem. Soc. 146 (2024) 7779–7790. doi: 10.1021/jacs.4c00429

  16. [16]

      H. Li, S. Li, R. Guan, et al., ACS Catal. 14 (2024) 12042–12050. doi: 10.1021/acscatal.4c03245

  17. [17]

      Y. Wu, M. Wang, Y. Tao, et al., Adv. Funct. Mater. 30 (2019) 1907120.

  18. [18]

      Y. Guo, C. Chen, Y. Li, et al., Appl. Surf. Sci. 623 (2023) 156995. doi: 10.1016/j.apsusc.2023.156995

  19. [19]

      X. Li, C. Chen, T. Gao, et al., J. Alloys Compod. 981 (2024) 173661. doi: 10.1016/j.jallcom.2024.173661

  20. [20]

      X. Cheng, F. Ran, Y. Huang, et al., Adv. Funct. Mater. 31 (2021) 2100311. doi: 10.1002/adfm.202100311

  21. [21]

      X. Wang, K. Yang, C. Ma, et al., Chem. Eng. J. 452 (2023) 139257. doi: 10.1016/j.cej.2022.139257

  22. [22]

      N. Zhang, S. Huang, Z. Yuan, et al., Angew. Chem. Inter. Ed. 60 (2021) 2861–2865. doi: 10.1002/anie.202012322

  23. [23]

      J. Zhou, F. Wu, Y. Mei, et al., Adv. Mater. 34 (2022) 2200782. doi: 10.1002/adma.202200782

  24. [24]

      Q. Cao, H. Gao, Y. Gao, et al., Adv. Funct. Mater. 31 (2021) 2103922. doi: 10.1002/adfm.202103922

  25. [25]

      Y. Zeng, X. Zhang, R. Qin, et al., Adv. Mater. 31 (2019) e1903675. doi: 10.1002/adma.201903675

  26. [26]

      Y. Zhou, X. Wang, X. Shen, et al., J. Mater. Chem. A 8 (2020) 11719–11727. doi: 10.1039/d0ta02791j

  27. [27]

      Z. Wang, J. Huang, Z. Guo, et al., Joule 3 (2019) 1289–1300. doi: 10.1016/j.joule.2019.02.012

  28. [28]

      Y. An, Y. Tian, Y. Li, et al., Chem. Eng. J. 400 (2020) 125843. doi: 10.1016/j.cej.2020.125843

  29. [29]

      F. Xie, H. Li, X. Wang, et al., Adv. Energy Mater. 11 (2021) 2003419. doi: 10.1002/aenm.202003419

  30. [30]

      F. Wang, O. Borodin, T. Gao, et al., Nat. Mater. 17 (2018) 543–549. doi: 10.1038/s41563-018-0063-z

  31. [31]

      X. Zheng, K. Xu, Y. Ma, et al., Adv. Energy Mater. 14 (2024) 2400038. doi: 10.1002/aenm.202400038

  32. [32]

      M. Wang, X. Zheng, X. Zhang, et al., Adv. Energy Mater. 11 (2021) 2002904. doi: 10.1002/aenm.202002904

  33. [33]

      Z. Ni, X. Liang, L. Zhao, et al., Mater. Chem. Phys. 287 (2022) 126238. doi: 10.1016/j.matchemphys.2022.126238

  34. [34]

      B. Lee, H.R. Lee, H. Kim, et al., Chem. Commun. 51 (2015) 9265–9268. doi: 10.1039/C5CC02585K

  35. [35]

      J. Lee, J.B. Ju, W.I. Cho, et al., Electrochim. Acta 112 (2013) 138–143. doi: 10.4097/kjae.2013.64.2.138

  36. [36]

      D. Wang, X. Guo, Z. Chen, et al., ACS Appl. Mater. Interfaces 14 (2022) 27287–27293. doi: 10.1021/acsami.2c06793

  37. [37]

      Y. Ma, X. Xie, R. Lv, et al., ACS Sustain. Chem. Eng. 6 (2018) 8697–8703. doi: 10.1021/acssuschemeng.8b01014

  38. [38]

      Z. Wang, Z. Ruan, Z. Liu, et al., J. Mater. Chem. A 6 (2018) 8549–8557. doi: 10.1039/c8ta01172a

  39. [39]

      Z. Wang, Z. Ruan, W.S. Ng, et al., Small Methods 2 (2018) 1800150. doi: 10.1002/smtd.201800150

  40. [40]

      M. Fayette, H.J. Chang, I.A. Rodríguez-Pérez, et al., ACS Appl. Mater. Interfaces 12 (2020) 42763–42772. doi: 10.1021/acsami.0c10956

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  Figure 1  Scanning electron microscopy (SEM) images of (a) S-GP and (b) S-GP@Zn. (c) Transmission electron microscopy (TEM), inset image is high-resolution transmission electron microscopy (HRTEM), and (d) EDS mapping of S-GP@Zn. (e) Fourier transform infrared (FT-IR) and (f) Raman spectra of O-GP, N-GP, S-GP, and P-GP. (g) S 2p spectrum of S-GP.

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  Figure 2  (a) The binding energy of Zn atom with graphene (G) and different functional groups. (b) The charge density differences for Zn²⁺ adsorbed on pyridinic S (Spd) group, the yellow and light royal blue areas present the negative and positive charge differences. Models of the electric field distributions for (c) Zn foil and (d) S-GP@Zn. SEM images of S-GP anode during the Zn plating process at 5 mA/cm² with (e) 5 mAh/cm², (f) 10 mAh/cm², and (g) 20 mAh/cm², and (h) the corresponding schematic diagram of morphology evolution.

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  Figure 3  Reversible Zn plating/stripping performance with Zn, O-GP@Zn, N-GP@Zn, P-GP@Zn, and S-GP@Zn anodes. (a) E_a values of different cells. (b) Comparison of voltage profiles at 0.5 mA/cm² with 0.25 mAh/cm². (c) Rate performance. (d) The corresponding exchange current densities (i₀). (e) Performance comparison chart with other works. (f) CE of Zn//Cu cells. (g) The corresponding voltage profiles at different cycles.

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  Figure 4  Electrochemical performance of flexible Zn-Mn battery. (a) CV curves. (b) Capacities at different current densities. (c) Ragone plots [33–40]. (d) Long-term cyclic stability. (e) Capacity retention of the Zn-Mn battery under different bending angles at 1.0 A/g.

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